Dear Editor: We are writing this letter because we have new observations in relation to our newly invented treatment method for the chronic painful tendon-sclerosing Polidocanol injections. The new observations are of importance for decision-making about repeated treatments. Using repeated ultrasound (US) and colour Doppler (CD) examinations day by day after instituted treatment, we have observed that there is initially (during 1–3 weeks) an increased intratendinous vascularity. This might very well be a response to the treatment (possibly a secondary intratendinous vasodilation) and should not be an indication for additional treatment. Consequently, we suggest that the proposals from our studies [1, 9], that there should be a 3–8 weeks period in between treatments, and that there should be no additional treatment if there is no pain during tendon loading activity, are followed. Pain together with neovessels should be the only indication for treatment. Interestingly, we have observed a similar increased intratendinous vascularity in the early period after instituting treatment with eccentric training.